Storage tank for liquid metal

ABSTRACT

A system for circulating heated liquid metal (e.g. metallic sodium) through a conduit arrangement wherein, for example, the liquid metal functions as a heat-exchanging medium and is alternately cooled and heated. The system includes a unitary liquid metal storing and circulating device having a tank for storing the liquid metal and a pump for circulating the liquid. The pump, which is immersed in the liquid in the tank, has a liquid flow-through bearing and means for removing excess liquid metal which flows through the bearing. Valves associated with the system have liquid metal flow-through seals; means is provided for removing liquid metal which has leaked through the valve seals and returning it to the tank by the pump. The pump chamber is substantially isolated from the liquid metal pool or bath in the tank, whereby the absorption of inert gas into the liquid metal bath is minimized.

United States Patent ubsek et al.

[ 51 Jan. 18, 1972 [54] STORAGE TANK FOR LIQUID METAL [72] lnventors:Frantisek Dubsek; Vaclav Tomes, both of Brno; Mojmir Nlgrin, Jaromer;Jiri Sobotka, Brno, all of Czechoslovakia [73] Assignee: Prvni brnenskastrojlrnn, Zavody Klementa Gottwalda narodni podnik, Brno,

Czechoslovakia [22] Filed: Dec. 29, 1969 [21] Appl. No.: 888,369

[52] US. Cl ..l65/l08, 222/385 [51] Int. Cl "F28! 13/06 [58] Field ofSearch ..222/385; 165/108 3,130,878 4/1964 Zimmermann ..222/385X PrimaryExaminer-Carroll B. Dority, Jr. Attorney-Arthur 0. Klein [57] ABSTRACT Asystem for circulating heated liquid metal (e.g. metallic sodium)through a conduit arrangement wherein, for example, the liquid metalfunctions as a heat-exchanging medium and is alternately cooled andheated. The system includes a unitary liquid metal storing andcirculating device having a tank for storing the liquid metal and a pumpfor circulating the liquid. The pump, which is immersed in the liquid inthe tank, has a liquid flow-through bearing and means for removingexcess liquid metal which flows through the bearing. Valves associatedwith the system have liquid metal flow-through seals; means is providedfor removing liquid metal which has leaked through the valve seals andreturning it to the tank by the pump. The pump chamber is substantiallyisolated from the liquid metal pool or bath in the tank, whereby theabsorption of inert gas into the liquid metal bath is minimized.

12 Claims, 3 Drawing Figures PATENTED JANIBIQTE 3,635,286

SHEET 1 OF 2 Inventor.

Want/56k Du BSEK acln wfik I I"! .Y] 456% ATTORNEY STORAGE TANK FORLIQUID METAL This invention relates to a system for circulating andstoring heated liquid metals. Among the liquid metals which theapparatus of the invention may handle, for example, liquid sodium,although it is not limited thereto. Equipment operating with liquidmetals consists generally of a heating surface where liquid metalabsorbs heat, and of an area where the liquid metal transfers the heatto another heat carrier, of circulating liquid metal pumps, of liquidmetal charging pumps, of flowmeters, of liquid metal piping, ofexpansion tanks, of liquid metal storage tanks, of liquid metal shutoffand control valves, of liquid metal filtering apparatus, of inert gasdistribution system and of cooling liquid distribution system.

In conventional layouts employed in heavy duty service, all theaforesaid elements are separately mounted in boiler houses; this is verydisadvantageous from the operational and safety point of view. It isfrequently necessary that the area where the liquid metal transfers heatis widely separated from devices which are to be cooled by liquid metal.Such separate location of the pumps, of the valves, of the cleaners andof the liquid metaltanks gives rise to problems in plant equipmentoperating with liquid metals. Such problems are the removing of the sealleakage of pumps, valves and flanges on the side of the liquid metal andproblems relating to the desire to eliminate the spaces in the liquidmetal circuit of which full advantage is not taken during the operation.Such spaces include those over the liquid metal level in the expansionand storage tanks. Moreover, the separate location of the aforesaidequipment assemblies for liquid metals complicates the control of theparticular equipment and does not insure the safety of its operation.

A liquid-metal-circulating and storing system according to the presentinvention has as an object the removal of these disadvantages; connectedto the liquid metal circuit there is a liquid-metal-circulating pump,which is built into and connected to the tank space by means of aflow-through seal. The liquid metal circuit, in order to take the volumethermal expansion of the charge of the liquid metal circuit, not onlyhas a built-in pump, but also shutoff and control valves. The liquidmetal circulating through the pump communicates with the .liquid metalcharge in the storage tank by means of a hydrostatic bearing; theliquidmetal flowing through the valves communicates with the same chargeby'means of a flowthrough seal so that the single seals of the pump andof the valves seal only the pressure of the inert gas whichfills thespace over the level of the liquid metal in the storage tank. Liquidmetal vented from the liquid metal circuit is introduced to the inertgas space of the storage tank. A liquid metal I cleaner isadvantageously connected in parallel with the storage tank. Thecirculating pump, valves and inlet and delivery piping of the pump arepreferably arranged in a section of the storage tank.

The liquid metal absorbs gas at a rate which increases with increasingagitation of the upper surface of the metal. Gas absorption through theupper surface of the liquid metal can be substantially reduced by meansof equipment (FIG. 2), the

main feature of which is a separating plate under the upper surface ofthe liquid metal. Stirring of the liquid metal caused by the pump outletand inlet takes place only under the separating plate; such stirring isnot carried over to the space above the plate.-The liquid metal pump inthe tank according to the invention has one shaft bearing situateddirectly in the liquid metal space. It operates at the temperaturecorresponding to the ambient temperature of the pumped liquid metal,

. which can, however, in some cases be extremely high and thus maydeleteriously affect the bearing material. The working The inventionwill be further described with reference to the accompanying drawingswhich are given by way of example and include: I

FIG. 1 is a schematic view in section of a first system in accordancewith the invention;

FIG. 2 shows a first variant of the pump in the tank; and

FIG. 3 shows a storage tank with a second variant of the pump.

In the system shown in FIG. 1, a storage tank 1 is connected to a liquidmetal circuit 2 by means of discharge or pressure piping 3 and inlet orsuction piping 4 connected to a pump 5 which is submerged in the storagetank ll. An upper branch 6 on tank 1 has an extension part 7 securedthereto. The pump 5 is mounted on supporting plate 8 which is sealed topart 7. A hood 9, which encloses an electric motor 10, provides an inertgas space 11 sealed from the surrounding atmosphere. Inert gas space 11is separated from the inert gas space 12 over the liquid metal level bya seal 14! around vertical pump shaft 15. An impeller 16, secured to thelower end of the pump shaft, is surrounded by a pump casing, as shown.The pump casing is mounted on the lower end of a tube 32 the upper endof which is affixed to plate 8. The liquid metal space within the pumpcasing selectively communicates with liquid metal space 13 in thestorage tank 1 by means of a check and shutoff valve 18 which isselectively operated by a linkage 26 having a control handle 26a. Whenvalve 18 is opened, it permits the pump to suck liquid metal from pool13 into the pump and thence into the conduit system 2. Liquid metaldelivered by pump 5 flows upwardly through conduit 3, through valve 3awithin tank extension 7, to the circuit 2 where it flows through aheat-absorbing heat exchanger 34, located at a distance from tank ll.After leaving heat exchanger 34, the cooled liquid metal flows to ametal heating heat exchanger 35 and thence into pump inlet conduit 4through a valve 19 within tank extension 7.

The lower end of pump shaft 15 is mounted in a flowthrough orhydrostatic bearing 17. Liquid metal which leaks through bearing 17wells up into tube 32 where it remains as a column in pressureequilibrium.

Inert gas is supplied to the space 12 in tank 1 above the liquid metal13 by a source 24a of inert gas under pressure, such source beingconnected to the tank 1 through a conduit 24. The liquid metal circuit 2is vented by a pipe 23 leading to a crossover fitting 24b and thence totank 1 through a valve 1% disposed within tank 1. The above-mentionedconduit 24 is connected to the tank l by way of crossover fitting 24b asshown.

A liquid metal cleaner 25 is connected between discharge conduit 3 andthe tank 1. Thus, there is an inlet valve 21a disposed within tankextension 7 connected to conduit 3 and an outlet valve 25a disposedwithin the tank 1 above the liquid metal space 13.

It is to be noted that valves 20, 20a, 20b, 3a and 25a are mountedwithin the tank 1, and have valve stems projecting outwardly through andsealed to the walls of the tank. The valves are provided with handwheels; the hand wheels of valves 20, 20a and 20b are designated with anadded a, whereas the hand wheels are designated with an added I).

The valves 20, 20a and 20!: are provided with flow-through seals 19, 19aand 19b, respectively. The same is true of valves 21a and 25a. Anyliquid metal which leaks through the flowthrough seals of all of suchfive valves falls into the pool 13 of liquid metal and is eventuallyreturned, as the need arises, to the conduit 2 through the valve 18.

In FIG. 2 there is shown an alternative pump arrangement 5 in thestorage tank 1 containing liquid metal 13. The suction branch 4} of thepump 5 discharges under the liquid metal level. The pump 5 sucks theliquid metal by suction branch 28 in the form of a shroud and dischargesit through the pipe 3 to the circuit 2. A separating plate 27 issituated under the liquid metal level in the storage tank 1. Thisseparating plate 27 prevents the stirring by the pump of the liquidmetal above the separating plate 27, and thus prevents the inert gasfrom being entrained by the liquid metal.

FIG. 3 shows a further variant of the system of the invention. The shaftof pump 5' is mounted with its lower part in an antifriction bearing 29which operates in the liquid metal 13 at relatively high temperatures.The cooler and purified liquid metal flows in the direction of the arrowfrom the liquid metal cleaner through the pipe 31 which is situatedabove the antifriction bearing 29. The liquid metal level in the pipe 32is higher than level H by a height h. Because of the pressuredifference, the cool liquid metal as e.g., sodium is forced through theantifriction (ball) bearing 29, which is thus kept at the lowertemperature than is the temperature of the pumped liquid metal 13; theantifriction bearing 29 is preferably protected from corrosion which maybe caused by impurities contained in the liquid sodium.

The system in accordance with the invention removes the difficultiesrelating to the seal leakage of the pump and valves for liquid metals;it removes the problems connected with expansion tanks; it utilizes tobetter advantage the circulating circuit for the liquid metal. it alsoutilizes the circulating pump as a feeding pump, improves the processingsafety and the controllability of equipment operating with liquidmetals, minimizes the absorption of inert gas by the liquid metalsurface in the tank, raises the permissible bearing load, and prolongsthe service life of the pump impeller bearing.

Although this invention has been illustrated and described withreference to a plurality of embodiments thereof, it is understood thatit is in no way limited to the details of such embodiments but iscapable of numerous modifications within the scope of the appendedclaims.

We claim:

1. A system for circulating oxidizable liquid metals through a conduitarrangement, comprising a unitary liquid metal storing and circulatingdevice having a tank liquid metal therein and a pump for circulating theliquid metal, the pump being disposed within the tank and pump dischargeand inlet conduits extending to the pump through the walls of the tank,and comprising a source of inert gas, means for introducing said inertgas into the space within the tank above the liquid metal.

2. A system for circulating heated liquids through a conduitarrangement, comprising a unitary liquid storing and circulating devicehaving a tank for storing the liquid and a pump for circulating theliquid, the pump being disposed within the tank and pump discharge andinlet conduits extending to the pump through the walls of the tank, thepump being immersed in the liquid, the pump having a pump shaftsupported in a liquid flow-through bearing, and means supplying liquidof lower than ambient temperature to the bearing.

3. A system for circulating heated liquids through a conduitarrangement, comprising a unitary liquid storing and circulating devicehaving a tank for storing the liquid and a pump for circulating theliquid, the pump being disposed within the tank and pump discharge andinlet conduits extending to the pump through the walls of the tank, thepump being immersed in the liquid in the tank, a horizontal plateseparating the space within the tank to an upper and a lower space, apump inlet means communicating with the lower space, and said inletconduit communicating with said lower space, whereby the liquid in theupper space is protected from being stirred by the action of the pump.

4. A closed pressure system for circulating liquid metal comprising aunitary liquid metal storing and circulating device having a tankcontaining liquid metal, means to introduce inert gas into the tank andprovide an inert atmosphere in the tank in the space above the liquidmetal therein, a conduit arrangement, a pump disposed within the tankand serving to feed liquid metal to the conduit arrangement as well asto circulate liquid metal therethrough, the conduit arrangementincluding pump discharge and inlet conduits extending to the pumpthrough the walls of the tank.

5. A system according to claim 4, comprising pump feeding conduit meanscommunicating with the liquid metal in the tank, discharge and returnconduit means, and valves within the tank interposed in said dischargeand return conduit means so that t e liquid metal leaking through theseals of the valves drips into the tank.

6. A system according to claim 4, wherein the pump is immersed in theliquid metal, and the pump has a pump shaft supported in a liquidflow-through bearing to which cooler liquid metal is supplied through aseparate conduit from a filter device connected in parallel with thetank, whereby the liquid metal flowing through the bearing has theimpurities removed therefrom in the filter device, whereby to preventthe bearing from corrosion.

7. A system according to claim 4, comprising piping connected to theouter conduit arrangement and leading to the tank for venting the outerconduit arrangement, whereby the tank may be used as a venting and anequalizing tank.

8. A system according to claim 1, comprising control, shutoff and safetyvalves interposed in the conduit arrangement, said valves being disposedwithin the tank and having valve spindles which pass through the wallsof the storage tank and are sealed thereto by means sealing against theescape of inert gas.

9. A system according to claim 8, comprising means for removing liquidwhich leaks from the valves and returning it to the pump.

10. A system according to claim 8, comprising an upstanding section ofthe tank above the liquid pool therein, and wherein delivery and inletvalves in the conduits in the tank are disposed in said upstandingsection.

11. A system according to claim 10, comprising a depending section ofthe tank in alignment with the upstanding section, the pump beingdisposed in said depending section and immersed in liquid therein.

12. A system according to claim 2, wherein the bearing is disposed atthe top of the pump, comprising a vertical tube surrounding the bearingand isolating it from the liquid in the pool in the tank and means forintroducing said cooler liquid into the tube.

a a a a:

1. A system for circulating oxidizable liquid metals through a conduitarrangement, compRising a unitary liquid metal storing and circulatingdevice having a tank liquid metal therein and a pump for circulating theliquid metal, the pump being disposed within the tank and pump dischargeand inlet conduits extending to the pump through the walls of the tank,and comprising a source of inert gas, means for introducing said inertgas into the space within the tank above the liquid metal.
 2. A systemfor circulating heated liquids through a conduit arrangement, comprisinga unitary liquid storing and circulating device having a tank forstoring the liquid and a pump for circulating the liquid, the pump beingdisposed within the tank and pump discharge and inlet conduits extendingto the pump through the walls of the tank, the pump being immersed inthe liquid, the pump having a pump shaft supported in a liquidflow-through bearing, and means supplying liquid of lower than ambienttemperature to the bearing.
 3. A system for circulating heated liquidsthrough a conduit arrangement, comprising a unitary liquid storing andcirculating device having a tank for storing the liquid and a pump forcirculating the liquid, the pump being disposed within the tank and pumpdischarge and inlet conduits extending to the pump through the walls ofthe tank, the pump being immersed in the liquid in the tank, ahorizontal plate separating the space within the tank to an upper and alower space, a pump inlet means communicating with the lower space, andsaid inlet conduit communicating with said lower space, whereby theliquid in the upper space is protected from being stirred by the actionof the pump.
 4. A closed pressure system for circulating liquid metalcomprising a unitary liquid metal storing and circulating device havinga tank containing liquid metal, means to introduce inert gas into thetank and provide an inert atmosphere in the tank in the space above theliquid metal therein, a conduit arrangement, a pump disposed within thetank and serving to feed liquid metal to the conduit arrangement as wellas to circulate liquid metal therethrough, the conduit arrangementincluding pump discharge and inlet conduits extending to the pumpthrough the walls of the tank.
 5. A system according to claim 4,comprising pump feeding conduit means communicating with the liquidmetal in the tank, discharge and return conduit means, and valves withinthe tank interposed in said discharge and return conduit means so thatthe liquid metal leaking through the seals of the valves drips into thetank.
 6. A system according to claim 4, wherein the pump is immersed inthe liquid metal, and the pump has a pump shaft supported in a liquidflow-through bearing to which cooler liquid metal is supplied through aseparate conduit from a filter device connected in parallel with thetank, whereby the liquid metal flowing through the bearing has theimpurities removed therefrom in the filter device, whereby to preventthe bearing from corrosion.
 7. A system according to claim 4, comprisingpiping connected to the outer conduit arrangement and leading to thetank for venting the outer conduit arrangement, whereby the tank may beused as a venting and an equalizing tank.
 8. A system according to claim1, comprising control, shutoff and safety valves interposed in theconduit arrangement, said valves being disposed within the tank andhaving valve spindles which pass through the walls of the storage tankand are sealed thereto by means sealing against the escape of inert gas.9. A system according to claim 8, comprising means for removing liquidwhich leaks from the valves and returning it to the pump.
 10. A systemaccording to claim 8, comprising an upstanding section of the tank abovethe liquid pool therein, and wherein delivery and inlet valves in theconduits in the tank are disposed in said upstanding section.
 11. Asystem according to claim 10, comprising a depending section of the tankin alignment with the upstanding section, the pump being disposed insaid dependiNg section and immersed in liquid therein.
 12. A systemaccording to claim 2, wherein the bearing is disposed at the top of thepump, comprising a vertical tube surrounding the bearing and isolatingit from the liquid in the pool in the tank and means for introducingsaid cooler liquid into the tube.